Tool and method for reaming and tapping a spark plug opening in a rotary engine housing

ABSTRACT

A tool and method for in-place reaming and tapping of a damaged spark plug opening in rotary engine housing for receipt of a threaded insert wherein an alignment block is secured by a bolt to an undamaged spark plug opening after a second opening of the alignment block is aligned with the aid of an alignment pin to the damaged spark plug opening. After the alignment pin is removed, the second opening of the alignment block is adapted to operatively receive seriatim a reamer assembly for reaming out the damaged threads of the spark plug opening and a tap assembly for tapping the reamed hole. Air is forced into the engine housing through a conduit in the securing bolt and passed outwardly through the flutes of the reamer and tap assemblies during the reaming and tapping operation to prevent metallic chips from falling into the engine housing and thereby damaging rotar seals.

United States Patent Heyworth et al.

[ Nov. 12, 1974 TOOL AND METHOD FOR REAMING AND TAPPING A SPARK PLUG OPENING IN A ROTARY ENGINE HOUSING [75] Inventors: Ernest Heyworth, Fullerton; Phillip Schwartz, Huntington Beach, both of Calif.

[73] Assignee: Tridair Industries, Redondo Beach,

Calif.

[22] Filed: Sept. 4, 1973 [21] Appl. No.: 394,035

[52] US. Cl 408/1, 29/401, 408/75,

[51] Int. C1...B23b 35/00, B23b 41/12, B23b 45/14 [58] Field of Search 408/1, 72, 79, 75; 29/401 [56] References Cited UNITED STATES PATENTS 1,597,468 8/1926 Holehouse 408/79 3,227,010 1/1966 Daubner et al. 408/1 3,750,259 8/1973 Timmons 29/401 3,800,391 4/1974 Westbrook 408/79 Primary ExaminerFrancis S. Husar Attorney, Agent, or FirmT. A. Seeman [57] ABSTRACT A tool and method for in-place reaming and tapping of a damaged spark plug opening in rotary engine housing for receipt of a threaded insert wherein an alignment block is secured by a bolt to an undamaged spark plug opening after a second opening of the alignment block is aligned with the aid of an alignment pin to the damaged spark plug opening. After the alignment pin is removed, the second opening of the alignment block is adapted to operatively receive seriatim a reamer assembly for reaming out the damaged threads of the spark plug opening and a tap assembly for tapping the reamed hole. Air is forced into the engine housing through a conduit in the securing bolt and passed outwardly through the flutes of the reamer and tap assemblies during the reaming and tapping operation to prevent metallic chips from falling into the engine housing and thereby damaging rotar seals.

10 Claims, 4 Drawing Figures TOOL AND METHOD FOR REAMING AND TAPPING A SPARK PLUG OPENING IN A ROTARY ENGINE HOUSING BACKGROUND OF THE INVENTION This invention relates to a tool and method for preparing a defective spark plug opening in a rotary engine housing for the receipt of a threaded insert; and more particularly, to a tool and method for preparing such a defective opening by reaming and tapping the same without the necessity of removing the engine from its installation and without the danger of metallic chips falling into the housing and possibly damaging rotor seals.

This housings of rotary engines are usually made of relatively soft material such as aluminum, consequently, the threads of the spark plug openings are susceptible to being damaged by repeated insertion and removal of the plugs. When damaged, the damaged threads must be reamedout and new threads tapped in the opening. A harder threaded insert, such as shown in U.S. Pat. No. 3,604,105,,may then be inserted into the tapped opening for receipt of the spark plug.

It is the object of this invention to provide a tool and method for preparing a damaged sparkplug opening in a rotary engine housing for the receipt of such a threaded insert and wherein the damaged opening may be easily parpared by unskilled personnel in a rapid and efficient manner without removing the engine and without damaging sensitive rotor seals by the contamination of metallic chips falling into the engine housing during the reaming and tapping operation.

SUMMARY OF THEINVENTION The elements of the tool generally comprise an alignment block, securing bolt, guide pin, and reamer and tap assemblies.

The alignment block has two cylindrical openings. It is secured to the engine housing by a securing bolt which extends through one opening into threaded engagement with an undamaged spark plug opening. Prior to the bolt being seated, the second threaded opening of the alignment block is aligned with and superimposed above an adjacent spark plug opening having damaged threads. To align the block in this position, the block is maneuvered by a guide pin, extending through the second alignment block opening, until the pin drops intothe damaged spark plug opening. Thereafter, the securing bolt is seated to clamp the block securely in place.

After the alignment block has been suitably clamped, the alignment pin is removed and a reamer assembly is installed in the threaded opening of the block. The reamer assembly comprises a reamer clamped to a bushing which is in turn threadably engaged with the threaded block opening. Rotation of the assembly feeds the bushing and included reamer into the spark plug opening and thereby reams out the damaged threads. A bellville washer, clamped between the bushing and the reamer, acts as a clutch means to enable the reamer to slip relative to the bushing when making a cut, which thereby regulates the infeed of the reamer into the spark plug opening.

After the damaged spark plug opening is reamed, the reamer assembly is removed anda tap assembly, comprising a tap and tap bushing, is inserted into the threaded opening of the alignment block. The tapis thereafter rotated to tap new threadsinto the reamed spark plug opening. Since the tap is of smaller diameter than the block opening, a smooth-wall, centeringbushing is inserted between the tap and the opening tocenter and support the tap while beingrotated.

During the reaming and tapping operation, air is forced through a centralair passagev of the securi'n'gbolt into the housing and out through the flutes of the reamer and taps respectively. This-prevents any metallic chips cut during the reaming or tapping operation from falling into the housing and thereby possibly damaging the rotor seals of therotary engine. Toinsure-that there is an adequate air passage for these chips tobe blown out during the reaming operation,,thealignment block is preferably spaced above the rotary housingby a spacing bushing, inserted-into the first-opening of the block and extending below therefrom intotcontactawith the housing.

After the defective spark-plugopening is tapped, the alignment block is removed -by unscrewing the securing bolt. A threaded insert of the type shown'in -U.S. Pat. No. 3,604,105 is then inserted intogtheenlarged tapped opening for the receipt of a sparkgplug.

The invention accordinglycomprises the features of construction, a combinationof elements, an arrangement of parts which can be-exemplifiedrinthe Construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE "DRAWINGS reamer assembly for-reamingout-the damagedthreads of the illustrated damaged sparkplug opening;

FIG. 3 is a partial front elevational view, partially in cross section, of the threaded second opening of the alignment-block of FIG. 1 in-combination-with atapfor tapping new threads in thedamagedsparkplug opening after being reamed; and,

FIG. 4 is a partial front-elevational view,'par.tialiy+in cross section, illustrating the damaged sparkplugopening of FIG. 1 after being reamed and tapped, and m-an exploded view, illustrating an insert of the type. intended to be inserted within the tapped opening,

Similar referenced characters refer tosimilar'aparts throughout views of the drawing.

DESCRIPTION or PREFERRED"EMBODIMENTS.

As illustrated, principal elements of the tool comprising my invention consist of an alignmentblock'2, a;se curing bolt 4, a hold-out bushing 6,. a, guide pin-i8, a reamer assembly 10, and a tap' assembly 12.

As best seen in the frontelevational view of FIG. 1,

alignment block- 2has a first cylindrical opening *l'4an'd a second threaded cylindrical opening 116. Each 'opening is suitably positioned and dimensioned for respective alignment with a first and second conventional sparkplug opening 18, 20 of a rotary engine housing 22. Alignment block 2 is cubic in dimension with a rectangular upper and lower face and of a size sufficiently large to support the spacing and location of alignment block holes l4, 16; yet sufficiently small in dimension so as to be installed on the outer surface of housing 22 without interference.

Rotary engine housing 22 is of the type frequently used in automotive applications. Interior wall 24, only a portion of which is shown, of engine housing 22 is eliptical and a rotor, not shown, rides about the wall in a conventional manner. Spacing of the rotor vanes is such that as the rotor rotates about the wall 24, the vanes form a combustion chamber to which at one point in time of rotation, sparkplug openings 18, 20, are in common communication.

Housing 22 is made from aluminum or other soft material. As a consequence the threads of the sparkplug openings are susceptible to being damaged by overtorquing the plug, by carbon at the end of the plug damaging the threads upon removal, and other similar causes. When the threads of the sparkplug opening are damaged, the threads must be reamed out and new threads tapped in the reamed opening. Since the opening is over-sized after this operation, an insert, of the type shown in the U.S. Pat. No. 3,604,105, is placed within the tapped opening for receipt of the sparkplug. The tool comprising this invention provides a means for preparing a damaged opening to receive the insert without damage to the engine and without the necessity of removing it from the automobile. For purposes of explanation, sparkplug opening 18 is considered normal while opening 20 is considered damaged and in need of repair.

The first opening 14 of the alignment block receives in a pressed-fit relationship, hold-out bushing 6. As can be easily seen in FIG. 1, the hold-out bushing, or spacer means, extends below the bottom surface of the block and butts against shoulder 26 of an enlarged counterbore formed in sparkplug opening 18. The extension of bushing 6 from the bottom of the alignment block is such that the alignment block is spaced from housing 22 when the bushing contacts shoulder 26. It is desirable to space the alignment block from the housing 22 to facilitate the passage of air and cut chips from the sparkplug opening 20 when the damaged threads are being reamed, as will be explained in more detail below, but it is not absolutely necessary that this spacing be provided.

Securing bolt 4 extends through hold-out bushing 6 and is threaded into the undamaged first sparkplug opening 18 to rigidly clamp the alignment block 2 to housing 22. Extending throughout the length of bolt 4 is a central bore 28 functioning to provide a means for passing compressed air into the housing 22. A threaded counterbore 30 is provided at the upper end of the bore 28 as an appropriate fitting for attachment to a compressed air line, not shown. A sealing washer 32 seals the space between the head of the bolt and the bushing 6.

Guide pin 8 is used to perfectly align the threaded opening 16 of the alignment block with respect to the damaged spark plug opening 18. Its diameter provides a sliding fit relationship between the pin and the alignment block opening, and it has a lower tapered end for self-centering insertion into the defective sparkv plug opening 20 as shown in FIG. 1. After the alignment block is suitably aligned, the securing bolt is seated to rigidly secure and clamp the alignment block 2 to hous ing 22 as seen.

Guide pin 8 is then removed and reamer assembly 10 is inserted into the threaded opening 16 of block 2 for reaming out the defective threads of the damaged spark plug opening 20, as seen in FIG. 2. The reamer assembly comprises a threaded bushing 36 clamped to a fluted reamer 38 by nut 40 and lock nut 42. A typical bellville washer 44, acting as a clutch means, is clamped between the nut 40 and bushing 36. As the reamer 38 is rotated by a driver, such as a wrench, it rotates bushing 36 downwardly to feed the lower cutting edges of the reamer into the damaged spark plug opening and to thereby ream out the damaged threads. Bushing 36 is clamped in combination with the bellville washer 44 in such a manner that upon a predetermined torque, reamer 38 will rotate relative to the bushing.

.This regulates the infeed rate of the reamer. In explanation, as reamer 38 is rotated and takes a cut of metal in the spark plug opening, it is preferably, to facilitate utility, that the reamer not advance further into the spark plug opening, that is, have the reamer at the same cutting level, until the metal is completely cut. This is accomplished by the clutch means. As the reamer is making its out, the resistance to downward movement of the reamer creates a torque between the reamer and the bushing that exceeds the clamping force or friction created by the bellville washer which in turn causes the reamer to slip relative to the bushing until the cut is complete. At this time, the resistance of the downward movement of the reamer is not adequate to overcome the clamping force between the bushing and the reamer, and the bushing carries the reamer forwardly to make the next cut. Thus, there is a grabbing and ungrabbing relationship between the reamer and the bushing during the reaming operation until spark plug opening 18 is completely reamed. The parts are arranged such that when the bushing bottoms out against counterbore 46, the cutting surface of the reamer has completely removed the damaged threads of the spark plug opening without the reamer extending into the opening further than absolutely necessary.

After the defective threads have been reamed out and the reamer assembly 10 removed from the threaded block opening 16, tap assembly 12 is inserted into the opening 1 as seen in FIG. 3. The assembly comprises a fluted tap 48 and a cylindrical tap bushing 50. Since the diameter of the tap is substantially less than that of the threaded opening 16, tap bushing 50 is provided to support and center tap 48 during the tapping operation. There is a sliding fit between bushing 50, block opening 16 and tap 48. New threads are tapped into spark plug opening 20 by rotation of tap 48 by a drive tool, such as a wrench, in a conventional manner.

During the reaming and tapping operation, it is desirable to prevent metallic chips from falling into the interior of the housing and thereby possibly damaging the sensitive seals of the rotor vanes. To preventthis, air is forced into the combustion chamber through the air passage or bore 28 of the securing bolt 4 by a compressed air line, not shown, attached to the upper end of the bolt. The compressed air enters the chamber of the rotary engine housing and then is passed outwardly through the flutes of reamer 38 and tap 48. The air is under a sufficient pressure and velocity to carry the chips outwardly and thus prevents them from falling within housing 22.

In addition, during the reaming operation, the spacing of alignment block 2 from housing 22 allows the metallic chips to pass out between the alignment block and housing 22 as well as through the flutes and out through the top of the reamer.

When the tapping operation is complete, the alignment block is removed from the housing and the newly tapped spark plug opening 20, as shown in FIG. 4, is ready to receive a hard, threaded insert 52, of the type described in US. Pat. No. 3,604,105, for receipt of a spark plug.

It should now be evident that a new and novel tool and method for preparing a damaged spark plug opening in a rotary engine housing for the receipt of a threaded insert has been provided. The tool and method allows a damaged spark plug opening to be easily repaired by unskilled personnel in a rapid and efficient manner without removing the engine and without damaging sensitive rotor seals by metallic chips falling into the housing during the reaming and tapping operation. Moreover, the tool is economical and feasible to manufacture.

Although I have typically described certain specific embodiments in my invention, it is of course understood that the invention is not limited to these particular forms but rather as applicable in numerous variations falling within the scope of the appended claims.

I claim:

1. A tool for preparing a damaged spark plug opening in a rotary engine housing for the receipt of a threaded insert comprising, an alignment block having a first and second opening for respective alignment with undamaged and damaged spark plug openings in communication with a common combustion chamber in said rotary engine, a securing bolt for clamping said alignment block to said housing, said bolt adapted to extend through said first opening of said alignment block and into threaded engagement with said undamaged spark plug opening, said bolt having air conduit means for communication with said combustion chamber, and said alignment block opening having means to receive seriatim a reamer for reaming out damaged threads of said damaged spark plug opening and a tap for tapping new threads in the damaged opening after being reamed.

2. The tool of claim 1 wherein said air conduit means in said bolt comprises a central bore extending through the bolt with an upper section of the bore adapted for attachment to a compressed air line.

3. The tool of claim 2 further including spacer means for separation of said bloc-k relative to said housing.

4. The tool of claim 3 wherein said spacer means comprises a bushing retained within said first alignment block opening and extending below said block for supporting said alignment block above said rotary engine housing.

5. The tool of claim 1 wherein said second opening of said alignment block is threaded and the tool is in combination with a reamer assembly, said reamer assembly comprising a reamer clamped to a threaded bushing in turn removably threaded to the second alignment block opening such that rotation of said Y reamer rotates said bushing and included reamer through said threaded block opening, said reamer being fluted substantially throughout its length for passage of air and metallic chips, and said reamer having clutch means whereby rotation of said reamer rotates said bushing until the advent of a predetermined restraining force between the bushing and the reamer at which time said clutch means rotatably releases said reamer relative to said bushing.

6. The tool of claim 1 in combination with a tap asi sembly, said tap assembly comprising a tap fluted substantially throughout its length for passage of air and metallic chips and disposed within a tap bushing slidably-carried within said second alignment block opening for aligning said tap with the'damaged spark plug opening.

7. The tool of claim 1 in combination with alignment means for aligning said second alignment block openment with said undamaged spark plug openingfor attachment of said alignment block to said housing, said bolt having a central air passage extending throughout its length with an upper section adapted to receive a compressed air line; spacer means between said alignment block and said housing for spacing the block relative to said housing, alignment means foraligning said alignment block openings with said spark plug openings prior to said housing, said second alignment block opening being threaded and having means to receive seriatim a reamer assembly for reaming out said damaged spark plug opening and a tap assembly for tapping the threads in said damaged spark plug opening after being reamed, said reamer assembly comprising a reamer clamped to a threaded bushing with said threaded bushing being removably threaded to the second alignment block opening, said reamer being fluted substantially throughout for passage of air and metallic chips, and said reamer having clutch means whereby rotation of said reamer rotates said bushing and feeds said reamer into said damaged spark plug opening until the advent of a predetermined restraining force between the bushing and the reamer, said tap assembly comprising a tap and'tap bushing, said tap bushing slid- I ably received within said second opening of said alignment block and said tap being aligned with the damaged spark plug openings by extending through said bushing, and said tap being fluted substantially throughout its length for the passage of air and metallic chips.

10. A method of preparing a spark plug opening in a rotary engine housing for receipt of a threaded insert comprising, reaming out the thread of said opening, tapping new threads in said opening after being reamed and forcing air outwardly from said-housing through said opening while being reamed and tapped in a manner to prevent metallic chips from falling into said housing. 

1. A tool for preparing a damaged spark plug opening in a rotary engine housing for the receipt of a threaded insert comprising, an alignment block having a first and second opening for respective alignment with undamaged and damaged spark plug openings in communication with a common combustion chamber in said rotary engine, a securing bolt for clamping said alignment block to said housing, said bolt adapted to extend through said first opening of said alignment block and into threaded engagement with said undamaged spark plug opening, said bolt having air conduit means for communication with said combustion chamber, and said alignment block opening having means to receive seriatim a reamer for reaming out damaged threads of said damaged spark plug opening and a tap for tapping new threads in the damaged opening after being reamed.
 2. The tool of claim 1 wherein said air conduit means in said bolt comprises a central bore extending through the bolt with an upper section of the bore adapted for attachment to a compressed air line.
 3. The tool of claim 2 further including spacer means for separation of said block relative to said housing.
 4. The tool of claim 3 wherein said spacer means comprises a bushing retained within said first alignment block opening and extending below said block for supporting said alignment block above said rotary engine housing.
 5. The tool of claim 1 wherein said second opening of said alignment block is threaded and the tool is in combination with a reamer assembly, said reamer assembly comprising a reamer clamped to a threaded bushing in turn removably threaded to the second alignment block opening such that rotation of said reamer rotates said bushing and included reamer through said threaded block opening, said reamer being fluted substantially throughout its length for passage of air and metallic chips, and said reamer having clutch means whereby rotation of said reamer rotates said bushing until the advent of a predetermined restraining force between the bushing and the reamer at which time said clutch means rotatably releases said reamer relative to said bushing.
 6. The tool of claim 1 in combination with a tap assembly, said tap assembly comprising a tap fluted substantially throughout its length for passage of air and metallic chips and disposed within a tap bushing slidably carried within said second alignment block opening for aligning said tap with the damaged spark plug opening.
 7. The tool of claim 1 in combination with alignment means for aligning said second alignment block opening with said spark plug opening.
 8. The tool of claim 7 wherein said alignment means comprises an alignment pin.
 9. A tool for preparing a damaged spark plug opening in a rotary engine housing for the receipt of a threaded insert comprising, an alignment block having a first and second opening for respective alignment with an undamaged and damaged spark plug opening in said rotary engine housing, a bolt extending through said first opening of said alignment block into threaded engagement with said undamaged spark plug opening for attachment of said alignment block to said housing, said bolt having a central air passage extending throughout its length with an upper section adapted to receive a compressed air line; spacer means between said alignment block and said housing for spacing the block relative to said housing, alignment means for aligning said alignment block openings with said spark plug openings prior to said housing, said second alignment block opening being threaded and having means to receive seriatim a reamer assembly for reaming out said damaged Spark plug opening and a tap assembly for tapping the threads in said damaged spark plug opening after being reamed, said reamer assembly comprising a reamer clamped to a threaded bushing with said threaded bushing being removably threaded to the second alignment block opening, said reamer being fluted substantially throughout for passage of air and metallic chips, and said reamer having clutch means whereby rotation of said reamer rotates said bushing and feeds said reamer into said damaged spark plug opening until the advent of a predetermined restraining force between the bushing and the reamer, said tap assembly comprising a tap and tap bushing, said tap bushing slidably received within said second opening of said alignment block and said tap being aligned with the damaged spark plug openings by extending through said bushing, and said tap being fluted substantially throughout its length for the passage of air and metallic chips.
 10. A method of preparing a spark plug opening in a rotary engine housing for receipt of a threaded insert comprising, reaming out the thread of said opening, tapping new threads in said opening after being reamed and forcing air outwardly from said housing through said opening while being reamed and tapped in a manner to prevent metallic chips from falling into said housing. 